The hydraulic reciprocatory percussive means and the hydraulic rotary drive means are normally connected in parallel hydraulically, which requires flow splitting valve arrangements which have to proportion the power between the reciprocatory percussive means and the rotary drive means. Such valve arrangements, particularly with a device the percussive section of which is sensitive to flow and/or pressure conditions, can be complex. In addition power may be wasted, for example with a restrictor in series with the rotary drive means to reduce the pressure applied thereto. It is an object of the invention to provide a device which obviates the need for such complex valve arrangements, and which rotates the tool intermittently on the rebound strokes thereof.
It is a characteristic of hydraulic percussive devices that there is a considerable feed back of energy at the commencement of the exhaust stroke. The resilience of the tool and striker produces rebound with a high pressure pulse at the commencement of the exhaust stroke, and this energy is normally dissipated by a restrictor which provides a back pressure which also controls the reciprocating frequency. A further object of the invention is to employ this normally wasted energy, or a portion thereof, to power the rotary drive means.